devstack exercise for deletion, dns checking

This adds record and domain deletion to the designate.sh devstack
exercise.  This also adds DNS checking for the domain/record operations,
to verify that the changes were made in DNS.  Some functions in
designate.sh were moved to lib/designate and refactored slightly.
This also removes some IPA variables that were refactored into a
backend specific file, and fixes a bug in the ipa backend file.

Closes-Bug: #1326141
Change-Id: Ibb86b0b237b3d73a145733bc88dbc18dddbc20f5
(cherry picked from commit 05291ddbf59f638870a561b1182908b676d92832)
Merge "devstack exercise for deletion, dns checking"